Tube structure



July 27, 1943.

K. MAYERS TUBE STRUCTURE Filed Jan. 15, 1942 Patented July 21,19 3 a "2,325,527" I TUBE- STRUCTURE. ken Ff Mayersg Somerville, N. J., assignor to I j"NationalfIlnionBadio Corporation, Elizabeth, N J ,a corporation of Delaware Application January 15, 1942, Seria lNo.426,925

' Claims. (clean- 215) ;This invention relates ;to: improvements;;in the eontactpin constructedxfor radio. vacuunr tubes and like apparatus, and more particularly to a contact pin constructed "to provide a more-positive tube base to contactpin seal. a a

Vacuumtubesarenow commonly constructed with glass bases and envelopes and with contact pins of relatively stiff wire which extend through an mp oved base to contact pin seal for a vacuum'tube. i

Still another object of the invention is to increase the-reliability and. strength of the base to contact pin seal in a vacuum tube.

' A. further object of theinvention isto' provide a contact pin for a vacuum tube on which lonthe tube base to the interior of the tube where they serve as electrode supports or connecting wires. The contact pins are sealed into the glass base and are thus supported thereby. While a metal base cap is used to support the tube as a whole, this cap is necessarily insulated and spaced from the contact pins. Accordingly, the contact pins have relatively little support, and upon the placement of a tube into a conventional socket, each pin is subjected to considerable stress which tends to break theseal between the glass base and the contact pin. This tendency may be increased and may be particularly harmful in the case of a slightly misaligned contact pin or socket contact. Further, contact pins are now commonly formed of a reasonably hard and stiff steel or alloy wire formed, for example, by drawing the wire through a proper die. Such wire is likely to bear a die' scratch in the form of a slight shallow groove extending longitudinally on the surface of the Wire, or it may have longi-' tudinal seams resulting from elongation of gas bubbles or oxides in the original billet of steel or alloy, or surface cracks of any other origin. When contact pins are formed from such wire, one of the several pins used in each tube may have a longitudinal scratch which extends substantially entirely through the glass seal formed between the'tube base and the contact pin;

In some instances, the seal at the contact pin has been found initially to be air tight such that upon evacuation of the tube a satisfactory test could be obtained. However, when the tube was inserted into a socket, the strain thus encountered would very slightly break the glass to pin seal along the longitudinal scratch. Such a tube would then develop'a slight air leak which would render the tube useless. In other instances, due to the irregularity of the surface, as a result of the above described surface cracks or seams, an air-tight seal cannot be formed and a very minute air passage will result.

It is the principal object of the present invention to eliminate thedefects above mentioned by providing a novel contact pin to which a secure glass seal may be effected.

' Another object of the invention is to provide of these grooves 1, any lengthwise passages are 40.

gitudinal die scratches, surface cracks, or seams are not detrimental.

Other objects and advantages of the invention will be apparent from the following description.

In the drawing:

Fig. 1 is an enlarged elevation of the lower por- 7 tion of a vacuum tube having a portion broken awayto illustrate the present invention; and

Fig. 2 isa bot-tom planview of the tube of Fig. 1, the line :c-rcof Fig. 2 indicating the portion of the tube broken awayin Fig. 1.

The vacuum tube illustrated comprisesa glass envelope 1 having an integral base portion 2 which is materially thicker than the side walls of the envelope. To support the tube, a metal base 3 having a central supporting pin 4 is normally fitted onto the envelope base.

A number of contact pins 5, usually eight, are

provided. These pins extend through the base to eliminate sharp corners, and of a depth substantially greater than that of any longitudinal scratches which may be on the pins. By virtue efiectively blocked by a secure seal, and, further,

the seal thus formed is not susceptible to fracture as is the seal in a shallow, sharp cornered, irregular scratch.

By way of example, two axially spaced circumferential grooves about five or ten thousandths of an inch deep and semi-circular in section cut in a contact pin having a diameter of about fifty thousandths of an inch have proved very satisfactory, and tubes embodying such contact pins are entirely reliable. Preferably, two pairs of grooves are provided in each pin, having the same disposition in relation to the opposite ends of the pin, so that either pair of grooves may be used. This facilitates manufacture of the tube, as it eliminates the necessity of pre-arranging the pms.

It is to be understood that the invention is not limited to the particular structure shown nor to the dimensions set forth above, but is capable of various modifications Within the scope of the appended claims.

I claim: V

1. In avaeuum tube, an evacuated envelope having a relatively thick portion formed entirely of a single fusible material, a plurality of contact,

about the pin which is unaffected by the presence of a surface scratch.

2. In a vacuum tube, an evacuated envelope having a relatively thick portion formed entirely of a single fusible material, a plurality of solid smooth-surfaced cylindrical contact pins extending from the exterior of said envelope through said portionto, the interior ofsaidenyelope, and directly engagi said 5 material, the maintenance of the vacuum Within said envelope being depend- 1 cut upon the establishment and maintenance of pins extending from the exterior of said envelope sunk; seal being susceptible to breakage thereof through said portion to the interior of (ant-'-v 1 and preventing suchbreakage thereof, said means breakage thereof along a longitudinal surface scratch on any one of said pins, and means for maintaining said seal ancl-preventing. such break age thereof, said means comprising atleastone circumferential groove on eachz'pin locatedentirely within saidportion andafilled-with: sairijma- 'terial, said groove being of sufficientdepth so-t'nat the material therein forms: a permanent seal a direct seal between said pins and said material,

along a longitudinalsurface scratch on any one ofi'said pins, and means for maintaining said seal comprising at least one circumferential groove oneaeh pin locatedientirely within said portion and filled with said material, said groove being ofsufli'cient depth so that the material therein forms: a: permanent seal about; the pinwhich is unaffected by: thepresence: of a. surface scratch, each of pins being of substantially uniform diameter throughout its. length. except; for: the reduced diameter: at midi-8160MB; 

